The invention relates to methods and additives for improving the stability and appearance of paraffin candles, and most particularly relates, in one non-limiting embodiment, to methods and additives for inhibiting the separation of oils from paraffin candles.
Modern candles are primarily made of paraffin waxes obtained as a by-product of petroleum refining operations. Paraffin waxes are generally white, translucent, tasteless, odorless solids consisting of a mixture of solid hydrocarbons of relatively high molecular weight. Stearin is often added to the paraffin wax to create stronger candles and stearic acid is a candle additive used to harden and opacify wax. VYBAR 103(copyright) Polymer and VYBAR(copyright) 260 Polymer are two common additives in modern paraffin modification used for but not limited to the following purposes, stabilizing oil in paraffin, increasing opacity, and increasing hardness. VYBAR 103(copyright) Polymer is a poly (alpha olefin) additive with a molecular weight (Mn) of about 4400 available from Baker Petrolite. VYBAR 260(copyright) Polymer is a poly (alpha olefin) additive with a molecular weight (Mn) of about 2600 available from Baker Petrolite.
Because paraffin wax is odorless, fragrances or essential oils are often added to provide a scent or pleasing aroma during burning, and because paraffin waxes are colorless, they are often colored using liquid dyes. Powdered dyes are also used, although typically the powdered dyes are solubilized in an oil solvent than is blended with the paraffin wax. In the context of this invention, liquid oil dyes are defined to include solubilized powdered dyes. In some cases, powdered dyes and/or pigments are blended directly with the paraffin wax. To be compatible with the paraffin waxes, the liquid dyes are generally oil-based. However, there is a limit to the amount of essential oil and/or oil-based dye that may be added to a paraffin wax candle before separation of the oil occurs at room temperature. Oil separation is undesirable because it removes the oil from the candle making it unavailable for scenting the air, mars the appearance of the candle and makes it unattractive for salexe2x80x94particularly if the oil is carrying dye, and creates a nuisance that must be cleaned up. Typically, the oil xe2x80x9cbleedsxe2x80x9d or rises to the top (or surface) of the candle or object and pools at the top in a relatively short amount of time.
The oil separation problem is particularly aggravated in mottled candles. Mottling of waxes has been used to produce a variety of different textures and appearances to candles. Mottling within the context of this invention is the formation of small, generally white inclusions in the paraffin wax that contrast with a background color. The inclusions are relatively small, usually less than 1 mm, and are often described as xe2x80x9cflowersxe2x80x9d, xe2x80x9csnowflakesxe2x80x9d, xe2x80x9cstarburstsxe2x80x9d, and xe2x80x9csnow spottingxe2x80x9d. Mottling is not to be confused with fractures and cracks that appear from quench cooling of a candle.
To achieve the mottling appearance on the candle surface, some form of liquid phase should be present, and generally the fragrance oil and/or oil dye is used, although soft wax components that are liquid at room temperature or mineral oil may be used. Relatively slow cooling of the candle is also generally necessary for mottling to occur on the candle surface. For instance, if paraffin wax is melted at 75xc2x0 C. (167xc2x0 F.) and mixed with 5 wt % commercially available fragrance and/or dye and then slowly cooled to room temperature, mottling will occur. One non-limiting explanation for the mottling phenomenon is as follows. Wax crystals begin to nucleate at about 60xc2x0 C., leading to the production of larger, needle-like crystals that grow in breadth and length as crystallization progresses. At the solid-solid transition point of about 40xc2x0 C., the point at which solid wax re-crystallizes, contractions in the crystalline boundaries are thought to cause microcracks and bubbles. A vapor phase, which may be air, propagates through the wax during this solid transition displacing the liquid oils in the crystalline interstices. Mottling occurs as larger gaps occur between crystals. Light refraction at the crystal surfaces gives a white snowflake pattern characteristic of mottling. Increasing the liquid phase reduces the cohesive forces between crystals thereby permitting the creation of more voids causing increased mottling.
To obtain a highly fragranced candle, a deeply colored candle (color intensity can be manipulated independent of concentration and can be a powder additive) and/or a mottled candle, it is necessary to use liquid additives, particularly liquid oil additives (oil additives liquid at ambient temperature). Paraffin with a high oil content will mottle but this is not a common commercial practice. However, these same oils tend to undesirably separate from the paraffin wax at room temperature. Thus, it would be desirable if some technique or additive could be provided that would prevent or inhibit the separation of liquid oil additives from paraffin waxes and yet would encourage or not inhibit a mottling effect.
An object of the invention is to provide a method for forming paraffin objects, such as candles, which contain oils, but where the object has a reduced tendency for the oil to separate from the paraffin wax.
Another object of the invention is to provide a candle or other paraffin object containing an oil that is normally liquid at room temperature (such as to provide a fragrance and appearance effect, e.g. color and/or mottling), where the oil is inhibited from separating from the paraffin wax when the object is stored at room temperature. The invention is particularly addressed to paraffin objects where a fragrance and an appearance effect are coupled in the same object.
In carrying out these and other objects of the invention, there is provided, in one form, a method of making a paraffin object by combining a paraffin wax with at least one oil that is liquid at ambient temperature, and an amount of an additive effective to inhibit separation of the oil from the paraffin wax, where the additive comprises a branched poly(alpha olefin). The invention also involves objects made by this method. It will be appreciated that while the inventive method may be used to make candles, it may also be used to make other paraffin objects containing an oil where it is desired to prevent separation of the oil from the paraffin wax. The paraffin objects have a mottled appearance.